https://doi.org/10.1007/s100530170182
Isotope dependent predissociation in the C1Σ+, v=0 and v=1 states of CO
1
Laboratoire PhLAM, Université des Sciences et Technologies de
Lille, 59655 Villeneuve d'Ascq, France
2
Department of Physics and Astronomy, Laser Centre Vrije Universiteit,
De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
3
Department of Physics, Lund Institute of Technology,
P.O. Box 118, 22100 Lund, Sweden
Corresponding author: a wimu@nat.vu.nl
Received:
21
December
2000
Revised:
26
March
2001
Published online: 15 July 2001
Rotationally resolved spectral lines in the band of carbon
monoxide are investigated under high resolution using a coherent
vacuum ultraviolet laser source, continuously tunable near 107 nm.
Transition frequencies are determined by calibrating against a
reference standard of iodine lines, recorded with saturation spectroscopy
in the visible range, yielding an absolute accuracy of 0.003 cm-1
in the vacuum ultraviolet. Improved molecular constants
for the excited state are derived and no effects of perturbation
are found at the present level of accuracy.
Line broadening measurements result
in information on the excited state lifetime of the
state
for five natural isotopomers of carbon monoxide:
ps,
ps,
ps,
ps, and
ps.
Within the accuracy of the present measurements no effects of
J-dependent lifetimes were observed, for neither of the isotopomers.
In addition direct time domain measurements of the lifetime
of the
and v=1 states of the main isotopomer
are performed in a pump-probe experiment using a picosecond
VUV-laser, yielding
ps for v=0
and
ps for v=1.
For
in 12C16O and 13C16O
the same lifetime is found; this lifetime matches experimental values
of the oscillator strength and hence supports previous results showing pure
radiative decay in this state; the error margins however do not exclude some
low level of predissociation.
The measurements indicate that the
state of the 13C18O isotopomer is predissociated with an estimated
yield of 17% (i.e. above the level of predissociation for 12C16O.)
From the combined data predissociation yields upon excitation of the
state are derived, lying in the range 0.84-0.91
for the five less abundant isotopomers; for the main 12C16O
isotopomer a strongly deviating predissociation yield of 0.65 is deduced.
PACS: 33.20.Ni – Vacuum ultraviolet spectra / 33.80.Gj – Diffuse spectra; predissociation, photodissociation
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2001